While still a student at Dick Dowling Junior High School, he participated as a regular member of Beaumont High School's Royal Purple Band, and in May 1931 he took first place as trumpet soloist at the Texas Band Teacher's Association's Annual Eastern Division contest held in Temple, Texas.

His low range had a warmth associated with the cornet and even the flugelhorn, but this sound was underrecorded in favor of James' brilliant high register.

[9] With financial backing from Goodman,[10] James debuted his own big band in Philadelphia, Pennsylvania, in January 1939, but it didn't click until adding a string section in 1941.

[citation needed] He and his band appeared in four Hollywood films: Private Buckaroo and Springtime in the Rockies (both 1942), Two Girls and a Sailor (1944), and Best Foot Forward (1943).

The album from the movie charted at #1, with James backing big band singer and actress Doris Day.

[23] James's rigorous regime of practice as a child resulted in an exceptional technical proficiency in the more classical techniques of range, fingering and tonguing.

In 1940, James lost his contract with Columbia Records (he returned in 1941), and Frank Sinatra left the band that January.

Indeed, a U.S. Treasury report released in 1945 listed Harry James and Betty Grable as the highest-paid couple in the nation.

[26] While James remained commercially successful and personally committed to his music, some critics sought to find fault.

In Peter Levinson's 1999 biography, Dan Morgenstern, the respected critic and Director of the Institute of Jazz Studies, called the 1941 release of the later Grammy Hall of Fame inducted "You Made Me Love You" "the record that the jazz critics never forgave Harry James for recording.

James's jazz releases during this period, while not as numerous, include a variety of modern arrangements from Neal Hefti, Frank Devenport, Johnny Richards and Jimmy Mundy that often inspired his musicians, and as bop surpassed swing by the late 1940s, James was surprisingly open to its influence.

[31] While James never completely regained favor with jazz critics during his lifetime in spite of his return to more jazz-oriented releases in the late 1950s and into the 1960s, contemporary opinion of his work has shifted.

In 1972 while in London, he did an interview with the English jazz critic Steve Voce, who asked if the biggest audience was for the commercial numbers he had recorded.

His knowledge of horse racing was demonstrated during a 1958 appearance on The Lucy–Desi Comedy Hour entitled "Lucy Wins A Racehorse".

He played his last professional job, with the Harry James Orchestra, on June 26, 1983, in Los Angeles,[34] dying just nine days later in Las Vegas, Nevada[39] on July 5, 1983, at age 67.

Metronome magazine conducted annual readers' polls ranking the top jazz musician on each instrument.

The studio sessions were held in the years 1939–42, 1946–53, and 1956, and typically resulted in two tracks which allowed each participant a one chorus solo.

A similar annual readers' poll conducted by Downbeat magazine selected James as the best trumpet instrumentalist for the years 1937,[69] 1938[70] and 1939,[71] and as favorite soloist for 1942.